Field of the Invention
The present invention relates to a method for producing a Group III nitride semiconductor device, and more specifically, to a method for reducing a strain between a Group III nitride semiconductor and a transparent electrode.
Background Art
In the conventional method for producing a Group III nitride semiconductor light-emitting device, after the formation of the transparent electrode made of a material such as ITO and IZO on a p-type layer, heat treatment is performed to crystallize the transparent electrode. This improves the conductivity of the transparent electrode and reduces the light absorptivity.
Japanese Patent Application Laid-Open (kokai) No. 2014-154584 describes that the p-type layer and the transparent electrode are preferentially heated by microwave heating so as to activate the p-type layer and crystallize the transparent electrode at the same time.
However, as crystallization of the transparent electrode progresses by heat treatment, a strain is caused by different crystal structure or lattice mismatch between the p-type layer and the transparent electrode. Since the strain absorbs light, the emission efficiency was reduced.
A temperature suitable for crystallization of the transparent electrode is higher than the heat treatment temperature for p-type activation. However, heat treatment for p-type activation and crystallization of the transparent electrode are usually performed at the same time, considering thermal damage to the light-emitting layer or simplification of process. As a result, the transparent electrode is not sufficiently crystallized, and there was a room for improvement in conductivity or translucency.